The present invention relates generally to drop-on-demand technology capable of ejecting droplets of a flowable material, and more specifically to a flextensional transducer utilizing an ultrasonic metal welding technique to bond components together such that no adhesive or epoxy materials are necessary.
Inkjet printing is a technology that uses small drops of a flowable material, such as an ink droplet, to form an image on a medium. Two general types of inkjet printing technology exist, continuous flow technology and drop-on-demand technology. Continuous flow technology uses electrostatic acceleration and deflection to select ink drops from a continuous flow of ink to form an image. Drop-on-demand technology can be divided into two sub-categories, thermal inkjet technology and piezoelectric inkjet technology.
Thermal inkjet technology uses heat energy to vaporize a thin layer or bubble of ink which expels unvaporized ink above a resistive element and fires the ink through a nozzle. The physical components needed to implement thermal inkjet technology are embedded within an inkjet print cartridge. Conversely, piezoelectric inkjet technology includes an electromechanical means to eject a flowable material, such as an ink droplet. More specifically, an electrical signal is supplied to an orifice plate of a nozzle which forces a portion of the orifice plate to flex or contract into the nozzle, thereby causing an ejection of an ink droplet from the nozzle.
The frequency of a thermal inkjet printing device with which an ink droplet can be xe2x80x9cfiredxe2x80x9d is limited by the thermal characteristics of a resistive element of the thermal inkjet printing device. For example, conventional thermal inkjet printers are capable of firing at a frequency in the range of 1-100 kilohertz. Conversely, conventional piezoelectric inkjet printing devices are capable of at firing a frequency in the range of 7,500-15,000 kilohertz, or up to approximately 15 times faster than conventional thermal inkjet printing devices.
Conventional piezoelectric inkjet technology utilizes an adhesive bond, such as a glue or an epoxy, to bond several components of a flextensional transducer relating to fire of an ink droplet. For example, a piezoelectric body or ring is bonded to a transducer membrane, which is in turn bonded to a nozzle or an orifice plate of a nozzle. An adhesive or epoxy bond forms each of these connections. The piezoelectric body, transducer membrane, and nozzle each include an aperture through which the ink droplets are fired. These apertures are formed by a drilling process.
Ink droplets used in conventional inkjet printers are made up of various chemicals, some of which are extremely caustic. These caustic chemicals have a tendency to attack the adhesive bond layers of conventional inkjet printers such that the adhesive bond layers dissolve and a mechanical malfunction occurs. The erosion of the adhesive layers prevents the inkjet printer from properly operating.
In addition to the erosion of adhesive layers due to the caustic chemicals discussed above, conventional inkjet technology utilizing an adhesive bond layer suffers from numerous disadvantages such as the adhesives or epoxies require time during the assembly for cure, the adhesives or epoxies require a precise deposition, the thickness of an adhesive layer varies, thereby varying the frequency response time, and the adhesives or epoxies are poor electrical conductors, thereby inhibiting the performance of the overall inkjet printer.
There is a need for a flextensional transducer which eliminates the use of adhesives or epoxies to bond together various components of the flextensional transducer. Therefore, the materials ejected from the flextensional transducer, regardless of its chemical composition, will not attack and destroy the bond between various components, rendering the overall device inoperable.
The present invention is a flextensional transducer apparatus and method of fabricating a flextensional transducer apparatus capable of ejecting a flowable material, such as a droplet of ink. The present invention includes ultrasonically metal welding various components of the flextensional transducer to securely interconnect the components of the flextensional transducer. Thus, no adhesives, glues, or epoxies are used.
The method of fabricating the flextensional transducer capable of ejecting a flowable material includes ultrasonically metal welding an actuator body having an outer diameter and an aperture to a transducer membrane having an outer diameter and aperture. The transducer membrane is also ultrasonically metal welded to a nozzle capable of housing a portion of the flowable material. The nozzle includes a surface adjacent to the transducer membrane having an aperture. The flowable material can be ejected through the apertures in each of the layers onto a media.
In one preferred embodiment, the aperture in one or more of the layers are laser ablated prior to any ultrasonic metal welding. In another preferred embodiment, a layer of an ultrasonic weldable metal material, such as a layer of gold, silver, or brass, is deposited onto one or more surfaces of the actuator body, the transducer membrane, or the nozzle, prior to the ultrasonic metal welding of the components to ensure a proper bond. In yet another preferred embodiment, the method of fabricating the flextensional transducer further includes electrically coupling a first electrical lead to the actuator body while electrically coupling a second electrical lead to the nozzle. Electrical circuitry is electrically coupled to the first and second electrical leads and is capable of providing an electrical signal to the flextensional transducer. In response to the electrical signal, the actuator body and the transducer membrane flexes or contracts towards the nozzle, thereby ejecting the flowable material. In still yet another preferred embodiment, the method of fabricating the flextensional transducer further includes fluidly coupling a reservoir of the flowable material to the nozzle.
The flextensional transducer apparatus of the present invention is capable of ejecting a flowable material. The flextensional transducer apparatus includes an actuator body having an outer diameter and an aperture. A transducer membrane is associated with the actuator body. The transducer membrane has an outer diameter and an aperture. A nozzle is associated with the transducer membrane. The nozzle is capable of housing a portion of the flowable material and includes a surface adjacent to the transducer membrane having an aperture.
In one preferred embodiment, the outer diameter of the actuator body is smaller than the aperture in the surface of the nozzle adjacent to the transducer membrane. In another preferred embodiment, the actuator body is a piezo-ceramic ring.
The flextensional transducer apparatus utilizes no adhesives, such as glue or epoxies, to interface the actuator body with the transducer membrane or to interface the transducer membrane with the nozzle. Rather, an ultrasonic metal welding procedure is used.
In yet another preferred embodiment, an ultrasonic weldable metal material layer is fabricated onto one or more surfaces of the actuator body, the transducer membrane, or the nozzle.
In still yet another preferred embodiment, the flextensional transducer apparatus further includes a first electrical lead electrically coupled to the actuator body and a second electrical lead electrically coupled to the nozzle. Electrical circuitry is electrically coupled to the first and second electrical leads capable of providing an electrical signal to the flextensional transducer apparatus causing the actuator body and the transducer membrane flex or contract towards the nozzle. In a further preferred embodiment, the flextensional transducer apparatus includes a flowable material reservoir capable of housing the flowable material in fluid communication with the nozzle.
The present flextensional transducer provides several advantages over conventional flextensional transducers used in piezoelectric inkjet technology. First, the present invention produces a permanent bond without a significant heating. Heating can weaken various layers of a conventional transducer. Second, the present invention provides interconnection points between components which do not become brittle. Third, the present invention provides interconnection of components which are corrosion resistant. Fourth, the present invention provides good electric connectivity between components. Fifth, the present invention requires no consumable materials, such as adhesives or epoxies. Sixth, the present invention requires no special environmental conditions, such as a helium atmosphere or a vacuum, in the fabrication process. Seventh, the present invention provides the laser ablation process for machine holes in one or more of the components which can be precisely controlled, as compared to traditional machining processes, such as drilling.